[GRASS-user] Forward and backward RMS error.

Dear GRASS users and developers,

where can I find an explanation about the meaning of forward and backward

RMS errors in i.points? In the 6.4.3 and 6.5 manuals for i.points a unique value for RMS error is reported, but the two values are actually computed.

In 7.0 manual the two values are mentioned but no description of their meaning is reported.

How can the two values be used to evaluate accuracy in georectification? Which is used to rectify the map?

Many thanks in advance.

Aldo Clerici

Earth Sciences Dep.

Parma University